With mobile subscribers increasing, a requirement emerges for modern mobile communication systems to maintain high quality while enlarging the communication capacity. Among such attentions, multi-antenna technology arises as a hot issue in 3G mobile communication fields.
Multi-antenna technology, usually including spatial diversity and adaptive antenna technology, employs at least two antennas to receive signals in receiving directions and combines multiple parallel signals by processing methods such as diversity and beam forming, to achieve better performance than conventional uni-antenna.
Researches show that the introduction of multi-antenna can effectively increase SNR (Signal to Noise Ratio) of signals and thus greatly improve the communication quality during communication process. However, mobile terminals of current communication systems generally use the processing module for uni-antenna systems. If multi-antenna technology is to be applied in present mobile terminals, both the hardware and the software of the processing module need to be redesigned, which can be very expensive. Therefore, how to make modifications based on present mobile terminals and take full advantage of the hardware and software resources of the processing module of uni-antenna systems, comes as a key issue for multi-antenna to be applied in mobile terminals.
Now an example of a mobile terminal based on WCDMA (Wide-band Code Division Multiple Access) standard is given to show the makeup of the uni-antenna system in current mobile terminals and the challenges multi-antenna faced when applied to the said uni-antenna system.
FIG. 1 is a block diagram for a standard mobile phone with uni-antenna, comprising an antenna 100, a RF module 101, a RF interface module 102, a baseband MODEM module 103, and a system controller & source CODEC module 105. In the figure, the baseband MODEM module 103 may be composed of Rake receiver, spreading/de-spreading module, modulating/demodulating module and Viterbi/Turbo coding/decoding module; while system controller & source CODEC module 105 may be composed of controller and source coder/decoder.
In the downlink, radio signals received by antenna 100 are first amplified and down converted to IF (intermediate frequency) signals or analog baseband signals in RF module 101; then the IF signals or analog baseband signals are transformed to digital baseband signals to be inputted into baseband MODEM module 103, after being sampled and quantified in RF interface module 102; in baseband MODEM module 103, signals obtained from successive operations such as Rake reception, de-spreading, demodulating, de-interleaving, Viterbi/Turbo decoding, rate matching and etc, are provided to system controller & CODEC 105; in system controller & CODEC 105, the data processed by baseband MODEM module 103 will be further processed in data link layer, network layer or higher layer, including higher layer signaling processing, system control, source coding/decoding and etc.
Presently, the above uni-antenna mobile phone technology is quite mature indeed. Many manufacturers, including Philips, have developed sound chip-set solutions, where the function of the said baseband MODEM module 103 is generally realized by ASIC (application specific integrated circuits).
Whereas introducing the multi-antenna technology into present mobile phones will completely change the whole baseband module 103, whose hardware and corresponding software, such as Rake receivers, de-spreading and etc, can hardly be utilized. Therefore, how to make modifications based on present mobile terminals and effectively take advantage of the hardware and software resources in the processing module of uni-antenna systems, still remains as a problem to be settled for multi-antenna to be applied in mobile terminals.